1991518759 has 2 divisors, whose sum is σ = 1991518760. Its totient is φ = 1991518758.

The previous prime is 1991518757. The next prime is 1991518783. The reversal of 1991518759 is 9578151991.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1991518759 - 2¹ = 1991518757 is a prime.

It is a super-2 number, since 2×1991518759² = 7932293934897800162, which contains 22 as substring.

Together with 1991518757, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991518757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995759379 + 995759380.

It is an arithmetic number, because the mean of its divisors is an integer number (995759380).

Almost surely, 2^1991518759 is an apocalyptic number.

1991518759 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991518759 is an equidigital number, since it uses as much as digits as its factorization.

1991518759 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1020600, while the sum is 55.

The square root of 1991518759 is about 44626.4356519765. The cubic root of 1991518759 is about 1258.1375774934.

The spelling of 1991518759 in words is "one billion, nine hundred ninety-one million, five hundred eighteen thousand, seven hundred fifty-nine".